Method for activating double metallocyanide-compounds

ABSTRACT

The present invention relates to a process for reacting epoxides with an initiator compound in the presence of a double metal cyanide compound as a catalyst, said process having a shortened induction period, and the double metal cyanide compound being activated by adding the epoxide to a mixture of double metal cyanide compound and initiator compound at an internal reactor pressure of less than 1 bar, and also to the polyethers themselves obtainable by such a process.

The present invention relates to a process for reacting epoxides with aninitiator compound in the presence of a double metal cyanide compound asa catalyst, said process having a shortened induction period, and thedouble metal cyanide compound being activated by adding the epoxide to amixture of double metal cyanide compound and initiator compound at aninternal reactor pressure of less than 1 bar, and also to the polyethersthemselves obtainable by such a process.

The literature discloses that double metal cyanide compounds (DMCcompounds) may be used as catalysts for reacting initiator moleculeshaving active hydrogen with epoxides, for example in a polymerizationreaction. The ring-opening polymerizations of alkylene oxides aredescribed, for example, in EP-A 0 892 002, EP-1 0 862 977 and EP-A 0 755716. DMC compounds have a high catalytic activity in the polymerizationof epoxides. Nevertheless, the prior art discloses disadvantages ofthese catalysts, for example an induction period to be observed at thebeginning of the reaction.

An induction period means that the catalyst is not immediately active,but rather only attains its activity in contact with the initiatorcompound and the epoxide after a certain time. This induction periodmanifests itself in that, for example, after a small amount of epoxideis metered in, a certain pressure in the reactor results which remainsconstant for a certain time and falls quickly at the end of theinduction period. After the pressure drop, the catalyst is active andfurther epoxide can be metered in.

There is hitherto no known explanation for the reaction during thisinduction period. The induction period for activating a DMC compoundlasts, for example, for between a few minutes and a few hours. Thisinduction period leads to various problems when using DMC compounds ascatalysts. For instance, there is free epoxide in the reactor during theinduction period, which can lead to safety problems. This is the caseespecially when the catalyst does not light off despite very longwaiting times. Furthermore, free epoxide which is in the reactor at hightemperatures for a long time can enter into secondary reactions.

Examples of such secondary reactions include the isomerization of theepoxide to the corresponding aldehyde or a rearrangement to the allylalcohol. These secondary reactions lead to undesired by-products whichnecessitate a costly and inconvenient purification of the products.

Furthermore, a long induction period leads to a loss of reactor capacitywhich makes the process more expensive.

In order to remedy these disadvantages, various processes have alreadybeen described in the prior art which shorten the induction period whenactivating DMC compounds.

For instance, WO 98/52689 describes a process for shortening theinduction period in which, in addition to the conventional low-pressuretreatment of the initiator/DMC mixture, further measures for treatingthis mixture are carried out. An example of such a measure according toWO 98/52689 is the introduction of gaseous nitrogen. Such a processentails major technical alterations to the apparatus to be used.Furthermore, the time-consuming dewatering leads to loss of reactorcapacity which makes the product even more expensive.

WO 01/10933 describes a process for shortening the induction period inwhich the epoxide pressure in the reactor is kept constant bycontinuously metering in epoxide. This process also harbors the risk ofan accumulation of epoxide which in turn leads to the abovementionedproblems for safety and quality of the products.

It is an object of the present invention to provide, starting from theprior art, a process in which a shortening of the induction period isachieved without entailing major technical alterations in existingplants for DMC-catalyzed reaction of epoxides.

We have found that this object is achieved by a process for reactingepoxides with an initiator compound in the presence of a double metalcyanide compound as a catalyst, said process having a shortenedinduction period and comprising at least the stage (1):

-   -   (1) activating the double metal cyanide compounds by adding the        epoxide to a mixture of double metal cyanide compound and        initiator compound at an internal reactor pressure of less than        1 bar.

The metering of the epoxide into the evacuated reactor at an internalreactor pressure of less than 1 bar surprisingly achieves immediatelight-off of the reaction. This is all the more astonishing in that itis generally assumed that a certain elevated epoxide pressure isnecessary at the beginning of the induction period for the activation ofthe DMC compound. The elevated epoxide pressure was thought to lead toan increase in the solubility of the epoxide in the mixture of DMCcompound and initiator compound.

According to the invention, the internal reactor pressure on addition ofthe epoxide is less than 1 bar. In other words, after the conventionallow pressure treatment of the mixture of double metal cyanide compoundand initiator compound at elevated temperatures, the vacuum is onlypartially broken, if at all, for example using nitrogen, and the epoxideis then introduced into the reactor at the reaction temperature and aninternal pressure of less than 1 bar, preferably less than 500 mbar, inparticular less than 200 mbar, more preferably less than 100 mbar, forexample less than 50 mbar.

In a preferred embodiment, the present invention therefore relates to aprocess for reacting epoxides with an initiator compound in the presenceof a double metal cyanide compound as a catalyst, said process having ashortened induction period, and the internal reactor pressure at theaddition of stage (1) being less than 500 mbar.

According to the invention, it is also possible that, in addition to thelow pressure treatment of the mixture of DMC compound and initiatorcompound, further treatment steps are effected, as disclosed, forexample, in WO 98/52689.

Useful initiator compounds are any compounds which have an activehydrogen. According to the invention, preferred initiator compounds areOH-functional compounds.

According to the invention, examples of useful initiator compoundsinclude the following compounds: water, organic dicarboxylic acids suchas succinic acid, adipic acid, phthalic acid and terephthalic acid,aliphatic and aromatic, optionally N-mono-, N,N- andN,N′-dialkyl-substituted diamines having from 1 to 4 carbon atoms in thealkyl radical, such as optionally mono- and dialkyl-substitutedethylenediamine, diethylenetriamine, triethylenetetramine,1,3-propylenediamine, 1,3- or 1,4-butylenediamine, 1,2-, 1,3-, 1,4-,1,5- and 1,6-hexamethylenediamine, phenylenediamine, 2,3-, 2,4- and2,6-tolylenediamine and 4,4′-, 2,4′- and 2,2′-diaminodiphenylmethane.Further useful starting molecules include alkanolamines, e.g.ethanolamine, N-methyl- and N-ethylethanolamine, dialkanol-amines, e.g.diethanolamine, N-methyl- and N-ethyldiethanolamine, andtrialkanolamines, e.g. triethanolamine, and ammonia and also mono- orpolyhydric alcohols, such as monoethylene glycol, propane-1,2- and-1,3-diol, diethylene glycol, dipropylene glycol, butane-1,4-diol,hexane-1,6-diol, glycerol, trimethylolpropane, pentaerythritol, sorbitoland sucrose. The polyether polyalcohols used are preferably additionproducts of ethylene oxide and/or propylene oxide to water, monoethyleneglycol, diethylene glycol, propane-1,2-diol, dipropylene glycol,glycerol, trimethylolpropane, ethylenediamine, triethanolamine,pentaerythritol, sorbitol and/or sucrose, individually or in mixtures.

According to the invention, the initiator compounds may also be in theform of alkoxylates, in particular those having a molecular weight M_(w)in the range from 62 to 15 000 g/mol.

However, equally suitable are macromolecules having functional groupswhich have active hydrogen atoms, for example hydroxyl groups, inparticular those specified in WO 01/16209.

Especially preferred initiator compounds are monofunctional orpolyfunctional alcohols having from 2 to 24 carbon atoms, and particularpreference is given according to the invention to initiator compoundshaving from 8 to 15 carbon atoms, in particular from 10 to 15 carbonatoms, for example tridecanol.

Alcohols suitable according to the invention are thus in particularoctanol, nonanol, decanol, undecanol, dodecanol, tridecanol,tetradecanol, pentadecanol, iso-octanol, iso-nonanol, iso-decanol,iso-undecanol, iso-dodecanol, iso-tridecanol, iso-tetradecanol,iso-pentadecanol, preferably iso-decanol, 2-propylheptanol, tridecanol,iso-tridecanol or mixtures of C13- to C15-alcohols.

Useful DMC compounds are in principle any suitable compounds known tothose skilled in the art.

Examples of DMC compounds useful as catalysts are those described in WO99/16775 and DE 10117273.7. According to the invention, the double metalcyanide compounds of the general formula I in particular are used ascatalysts for the process according to the invention:M¹ _(a)[M²(CN)_(b)(A)_(c)]_(d)•fM¹ _(g)X_(n)•h(H₂O)•eL•kP  (I),where

-   -   M¹ is at least one metal ion selected from the group consisting        of Zn²⁺, Fe²⁺, Fe³⁺, Co³⁺, Ni²⁺, Mn²⁺, Co²⁺, Sn²⁺, Pb²⁺, Mo⁴⁺,        Mo⁶⁺, Al³⁺, V⁴⁺, V⁵⁺, Sr²⁺, W⁴⁺, W⁶⁺, Cr²⁺, Cr³⁺, Cd²⁺, Hg²⁺,        Pd²⁺, Pt²⁺, V²⁺, Mg²⁺, Ca²⁺, Ba²⁺, Cu²⁺, La³⁺, Ce³⁺, Ce⁴⁺, Eu³⁺,        Ti³⁺, Ti⁴⁺, Ag⁺, Rh²⁺, Rh³⁺, Ru²⁺ and Ru³⁺,    -   M² is at least one metal ion selected from the group consisting        of Fe²⁺, Fe³⁺, Co²⁺, Co³⁺, Mn²⁺, Mn³⁺, V⁴⁺, V⁵⁺, Cr²⁺, Cr³⁺,        Rh³⁺, Ru²⁺ and Ir³⁺,    -   A and X are each independently an anion selected from the group        consisting of halide, hydroxide, sulfate, carbonate, cyanide,        thiocyanate, isocyanate, cyanate, carboxylate, oxalate, nitrate,        nitrosyl, hydrogensulfate, phosphate, dihydrogenphosphate,        hydrogenphosphate and hydrogencarbonate,    -   L is a water-miscible ligand selected from the group consisting        of alcohols, aldehydes, ketones, ethers, polyethers, esters,        polyesters, polycarbonate, ureas, amides, primary, secondary and        tertiary amines, ligands containing pyridine nitrogen, nitriles,        sulfides, phosphides, phosphites, phosphines, phosphonates and        phosphates,    -   k is a fraction or integer greater than or equal to zero, and    -   P is an organic additive,    -   a, b, c, d, g and n are selected in such a way that the        electrical neutrality of compound (I) is ensured, where c may be        0,    -   e is the number of ligand molecules and is a fraction or integer        greater than 0 or is 0,    -   f, k, h and m are each independently a fraction or integer        greater than 0 or are 0.

Organic additives P include polyethers, polyesters, polycarbonates,polyalkylene glycol sorbitan esters, polyalkylene glycol glycidylethers, polyacrylamide, poly(acrylamide-co-acrylic acid), polyacrylicacid, poly(acrylamide-co-maleic acid), polyacrylonitrile, polyalkylacrylates, polyalkyl methacrylates, polyvinyl methyl ether, polyvinylethyl ether, polyvinyl acetate, polyvinyl alcohol,poly-N-vinylpyrrolidone, poly(N-vinylpyrrolidone-co-acrylic acid),polyvinyl methyl ketone, poly(4-vinylphenol), poly(acrylicacid-co-styrene), oxazoline polymers, polyalkylenimines, copolymers ofmaleic acid and maleic anhydride, hydroxyethylcellulose, polyacetates,ionic surface-active and interface-active compounds, bile acid or itssalts, esters or amides, carboxylic esters of polyhydric alcohols andglycosides.

These catalysts may be crystalline or amorphous. In the case that k isequal to zero, preference is given to crystalline double metal cyanidecompounds. In the case that k is greater than zero, preference is givento crystalline, semicrystalline and also substantially amorphouscatalysts.

There are various preferred embodiments of the modified catalysts. Onepreferred embodiment involves catalysts of the formula (I) where k isgreater than zero. The preferred catalyst then comprises at least onedouble metal cyanide compound, at least one organic ligand and at leastone organic additive P.

In another preferred embodiment, k is equal to zero, e is optionallyalso zero and X is exclusively a carboxylate, preferably formate,acetate and propionate. Such catalysts are described in WO 99/16775. Inthis embodiment, preference is given to crystalline double metal cyanidecatalysts. Preference is further given to double metal cyanide catalystsas described in WO 00/74845 which are crystalline and platelet-shaped.

The modified catalysts are prepared by combining a metal salt solutionwith a cyanometallate solution, each of which may optionally compriseboth an organic ligand L and an organic additive P. The organic ligandand optionally the organic additive are added subsequently. In apreferred embodiment of the catalyst preparation, an inactive doublemetal cyanide phase is first prepared and this is then converted to anactive double metal cyanide phase by recrystallization, as described inPCT/EP01/01893.

In another preferred embodiment of the catalysts, none of f, e and k areequal to zero. These are double metal cyanide catalysts which comprise awater-miscible organic ligand (generally in amounts from 0.5 to 30% byweight) and an organic additive (generally in amounts from 5 to 80% byweight), as described in WO 98/06312. The catalysts may either beprepared with vigorous stirring (24 000 rpm using Turrax) or withstirring as described in U.S. Pat. No. 5,158,922.

Useful catalysts for the process according to the invention are inparticular double metal cyanide compounds which comprise zinc, cobalt oriron, or two thereof. Particular preference is given, for example, toPrussian blue.

According to the invention, preference is given to using crystalline DMCcompounds. In a preferred embodiment, a crystalline DMC compound of theZn—Co type which comprises zinc acetate as a further metal saltcomponent is used as a catalyst. Such compounds crystallize in amonoclinic structure and have a platelet-shaped habit. Such compoundsare described, for example, in WO 00/74845 or PCT/EP01/01893.

DMC compounds useful as catalysts for the process according to theinvention may in principle be prepared by any means known to thoseskilled in the art. For example, the DMC compounds may be prepared bydirect precipitation, the incipient wetness method, or by preparing aprecursor phase and subsequent recrystallization.

For the process according to the invention, the DMC compounds may beused as powder, paste or suspension, or shaped to give a shaped body,incorporated into shaped bodies, foams or the like, or applied to shapedbodies, foams or the like.

The catalyst concentration used in the process according to theinvention, based on the final amount structure, is, according to theinvention, less than 2000 ppm, preferably less than 1000 ppm, inparticular less than 500 ppm, more preferably less than 100 ppm, forexample less than 50 ppm.

The epoxides used for the process according to the invention may inprinciple be any suitable epoxides. Examples of suitable epoxidesinclude C₂-C₂₀-alkylene oxides such as ethylene oxide, propylene oxide,1,2-butylene oxide, 2,3-butylene oxide, isobutylene oxide, penteneoxide, hexene oxide, cyclohexene oxide, styrene oxide, dodecene epoxide,octadecene epoxide and mixtures of these epoxides. Particularly suitableepoxides are ethylene oxide, propylene oxide, 1,2-butylene oxide,2,3-butylene oxide and pentene oxide, although particular preference isgiven to propylene oxide, 1,2-butylene oxide, 2,3-butylene oxide andisobutylene oxide.

In a preferred embodiment, the present invention therefore relates to aprocess reacting epoxides with an initiator compound in the presence ofa double metal cyanide compound as a catalyst, said process having ashortened induction period and the epoxide being propylene oxide orbutylene oxide or a mixture of one of these epoxides with at least onefurther epoxide.

According to the invention, after completed activation of the DMCcompound, the internal reactor pressure is brought to above 1 bar byadding inert gas, for example nitrogen. However, it is likewise possibleaccording to the invention that no additional inert gas is added afterthe activation.

In a further embodiment, the present invention therefore relates to aprocess for reacting epoxides with an initiator compound in the presenceof a double metal cyanide compound as a catalyst, said process having ashortened induction period and, after the activation of the double metalcyanide compound according to stage (1), the internal reactor pressurenot being increased by adding inert gas.

In an alternative embodiment, the present invention relates to a processfor reacting epoxides with an initiator compound in the presence of adouble metal cyanide compound as a catalyst, said process having ashortened induction period and, after the activation of the double metalcyanide compound according to stage (1), the internal reactor pressurebeing increased by adding inert gas.

Even in the case that no additional inert gas is added, the internalreactor pressure may rise toward the end of the reaction to internalreactor pressures of 1 bar or higher. This may result, for example, fromincreasing volume of the product or from traces of inert gas which maybe dissolved in the epoxide. The inert gases dissolved in the epoxideare not comprehended as additions of inert gas for the purposes of theinvention.

Within the scope of the present invention, preference is given to addingat least 5% of the total amount of epoxide used in the process at aninternal reactor pressure of less than 1 bar. This 5% of the totalamount of the epoxide used in the process may be added in its entiretyin the reaction of stage (1) or be divided between the reactions ofstage (1) and stage (2).

In a further embodiment, the present invention therefore relates to aprocess for reacting epoxides with an initiator compound in the presenceof a double metal cyanide compound as a catalyst, said process having ashortened induction period and at least 5% of the total amount of theepoxide used in the process being added at an internal reactor pressureof less than 1 bar.

According to the invention, preference is given to a process in whichthe addition of at least 5% of the total amount of the epoxide used inthe process is divided between the reactions of stage (1) and stage (2)at an internal reactor pressure of less than 1 bar.

When ethylene oxide is used in the process according to the invention,preference is given to metering some inert gas into the reactor, so thatthe internal reactor pressure is between 500 and 950 mbar.

According to the invention, the activation of the double metal cyanidecompound of stage (1) may be followed by a stage (2). According to theinvention, stage (2) comprises a reaction of the initiator compound withan epoxide in the presence of the activated DMC compound. The reactionof stage (2) may be, for example, the addition of one or more epoxidemolecules. Within the scope of the present invention, preference isgiven in particular to the reaction of stage (2) being a polymerizationof an epoxide in the presence of a DMC compound activated according tostage (1).

In a preferred embodiment, the present invention therefore relates to aprocess for reacting epoxides with an initiator compound in the presenceof a double metal cyanide compound as a catalyst, said process having ashortened induction period and the process comprising a stage (2):

-   -   (2) polymerizing an epoxide in the presence of a double metal        cyanide compound activated according to stage (1).

For the purposes of the present invention, the epoxide polymerized maybe any desired epoxide. According to the invention, it is possible thatthe second epoxide is different to the epoxide used for activating theDMC compound. However, it is equally possible for the purposes of thepresent invention that the epoxide used for activating the DMC compoundand the epoxide used for the polymerization are identical.

Furthermore, the present invention also relates to a polyetherobtainable by a process comprising the reaction of epoxides with aninitiator compound in the presence of a double metal cyanide compound asa catalyst, said process having a shortened induction period andcomprising at least the stage (1):

-   -   (1) activating the double metal cyanide compounds thereby adding        the epoxide to a mixture of double metal cyanide compound and        initiator compound at an internal reactor pressure of less than        1 bar.

In further preferred embodiments, the present invention relates topolyethers which were prepared using, as the epoxide, propylene oxide orbutylene oxide or a mixture of one of these epoxides with at least onefurther epoxide.

In a further embodiment, the present invention likewise relates topolyethers which were prepared using, as the initiator compound, amonofunctional or polyfunctional alcohol having from 2 to 24 carbonatoms.

The polyethers according to the invention or the polyethers preparedaccording to the invention may be used in particular as carrier oils,fuel additives, surfactants or polyethers for the polyurethanesynthesis.

The present invention is illustrated hereinbelow with the aid ofexamples.

EXAMPLES

Catalyst Synthesis:

In a stirred tank of capacity 30 l equipped with a propeller stirrer, animmersed pipe for metering, a pH probe and a scattered light probe, 16000 g of aqueous hexacyanocobaltic acid (cobalt content: 9 g/l) wereinitially charged and heated with stirring to 50° C. 9224 g of aqueouszinc acetate dihydrate solution (zinc content: 2.6% by weight) which hadlikewise been heated to 50° C. were then added within 15 minutes withstirring at a stirrer output of 0.4 W/l.

351 g of Pluronic® PE 6200 (BASF AG) were added to this precipitatesuspension and the mixture was stirred for a further 10 minutes.

A further 3690 g of aqueous zinc acetate dihydrate solution (zinccontent: 2.6% by weight) were then metered in within 5 minutes withstirring at a stirring energy of 1 W/l.

The suspension was stirred for a further 2 hours. Within this time, thepH fell from 4.02 to 3.27 and then remained constant. The precipitatesuspension obtained in this way was then filtered and washed on thefilter with 6 times the cake volume of water.

The damp filter cake was dried and dispersed in Tridekanol® N by meansof a slotted rotor mill. The resulting suspension had a multimetalcyanide content of 5% by weight.

EXAMPLE

In a 10 l autoclave equipped with a pitched-blade stirrer, temperaturemeasurement and epoxide metering, the amounts of initiator and DMCspecified in table 1 were initially charged. The initiator/DMC mixturewas subsequently dewatered at 100° C. under a vacuum of 10 mbar. Theautoclave was then brought to the reaction temperature specified intable 1. The amount of epoxide specified in table 1 was then meteredinto the evacuated autoclave. In these experiments, no induction periodwas observed. The reaction lit off immediately. The internal reactorpressure attained at the end of the reaction is reported in table 1.

Comparative Example

In a 10 l autoclave equipped with a pitched-blade stirrer, temperaturemeasurement and epoxide metering, the amounts of initiator and DMCspecified in table 1 were initially charged. The initiator/DMC mixturewas subsequently dewatered at 120° C. under vacuum (10 mbar). The vacuumwas then broken using nitrogen and the internal reactor pressure was setto a value of greater than 1 bar. The autoclave was then brought to thereaction temperature specified in table 1. The amount of epoxidespecified in table 1 was then metered into the autoclave. The inductionperiods observed can be found in table 1. The internal reactor pressureattained at the end of the reaction is reported in table 1. InitiatorEpoxide Catalyst Induction Internal amount amount amount Temperaturetime pressure Experiment Initiator [g] Epoxide [g] [g] [° C.] [min][bar] 1 Tridecanol 1200 PO 5220 1.3 140 0 1.8 2 Tridecanol 1200 PO 52200.3 140 1 1.8 3 Tridecanol 1200 BuO 5800 2.1 140 0 2.0 4 Tridecanol 1200BuO 5800 0.4 140 0 1.9 C1 Tridecanol 1200 PO 5220 1.3 135 15 4.3 C2Tridecanol 700 BuO 5542 0.3 100 20 4.8 C3 Tridecanol 700 BuO 5542 1.3145 90 5.4

1-6. (canceled)
 7. A process for reacting epoxides with an initiatorcompound in the presence of a double metal cyanide compound as acatalyst, said process having a shortened induction period andcomprising at least the stages (1) and (2): (1) activating the doublemetal cyanide compounds by adding the epoxide to a mixture of doublemetal cyanide compound and initiator compound at an internal reactorpressure of less than 1 bar, (2) polymerizing an epoxide in the presenceof a double metal cyanide compound activated according to stage (1),wherein at least 5% of the total amount of epoxide used in the processis added at an internal reactor pressure of less than 1 bar.
 8. Aprocess as claimed in claim 1, wherein the internal reactor pressure atthe addition of stage (1) is less than 500 mbar.
 9. A process as claimedin claim 1, wherein the internal reactor pressure is not increased byadding inert gas after the activation of the double metal cyanidecompound of stage (1).
 10. A process as claimed in claim 1, wherein theinternal reactor pressure is increased by adding inert gas after theactivation of the double metal cyanide compound of stage (1).
 11. Aprocess as claimed in claim 1, wherein the epoxide is propylene oxide orbutylene oxide or a mixture of one of these epoxides with at least onefurther epoxide.
 12. A process as claimed in claim 1, wherein theinitiator compound is a monofunctional or polyfunctional alcohol havingfrom 2 to 24 carbon atoms.